Hello,
We are working on a campus project that contains multiple NC and F&B CS buildings. We'll be registering the master site and the individual buildings under the campus approach. A centralized plant system (5 air cooled chillers connected to a CHW network) that is located on the roof of one of the buildings will be serving all buildings within the master site boundary. This even includes existing buildings that will not be targeting LEED certification within the master site.
Our understanding, based on the LEED V4 guidelines, is that each individual building will need to consider the plant system (upstream equipment) as a Campus Thermal Energy System (DC System) in the energy model. Is this correct?
If applying the campus thermal energy approach is correct, we would prefer to opt for path 2 (Full DES Performance accounting) instead of path 1 (purchased cooling); however we not have the the average SCOP of the air-cooled chiller system. The handbook states that default assumptions for COP and distribution losses can be used if average COP values are missing; however it does state that they "prefer" to see actual average COP values instead. Would it be permissable to use the default assumptions for the upstream equipment even if it is located within our site boundary, and we have information about the full load COP of the air cooled chiller equipment?
We appreciate your comments.
Michael Aghabi
January 14, 2020 - 8:10 am
Can anyone provide feedback about this?
Jamy Bacchus
Associate PrincipalME Engineers
20 thumbs up
January 24, 2020 - 11:58 am
There are a few layers here; let's start with your COP query on what values are permissible. The v4 Ref Guide states:
Equipment efficiencies, distribution losses, and distribution pumping energy may be determined using any of the following methods:
· Monitored data
· Engineering analysis
· Default values
So yes, you can use the default values for plant COP but you may not benefit or benefit much from them. Imagine the scenario where the baseline Appendix G plant is as-good or better, then you might find yourself needing the actual values to demonstrate that using Path 2 (or 3) for upstream equipment was a worthwhile endeavor.
As for your earlier question about modeling protocols, I would refer to the some older (2014) information from v2009 & v4 Campus Guidance. If you stick with Path 2 (or 3) and your district energy plant exports energy outside your LEED campus to other buildings, then you have to use the DES Guidance.
Hope this helps. I have a similar situation with the addition of a CHP using waste heat that I need to resolve.
Tyler Thumma
7GroupLEEDuser Expert
60 thumbs up
February 14, 2020 - 8:25 am
You are correct that each individual building will need to consider the plant system as a district energy system.
You are always permitted to use the default efficiencies, but they will likely result in lower performance than the actual efficiencies as the default values are conservative and are intended to represent a DES with relatively low efficiency.
One method for determining your actual COP would be the "engineering analysis", which would involve creating a model which included all of the buildings served by the plant and using this model to determine the annual efficiency. This is obviously considerably more effort than using the default values but may result in greater performance.